Python 3 - Second Edition

17.7    Keyword-Only Parameters

You can also define parameters that may be passed exclusively as keyword arguments. Such keyword-only parameters are separated by an asterisk (*) from the positional arguments:

>>> def f(*, c, d):...     print(c, d) >>> def g(a, b, *, c, d):...     print(a, b, c, d)  

In this case, the function f expects the keyword-only parameters c and d. In contrast to that, the function g expects in addition the positional parameters a and b. For both functions, there is no way to pass the c and d parameters except as keyword arguments:

>>> f(1, 2)Traceback (most recent call last):  File "<python-input-1>", line 1, in <module>    f(1, 2)    ~^^^^^^TypeError: f() takes 0 positional arguments but 2 were given>>> f(c=1, d=2)1 2>>> g(1, 2,